I suppose that jump-to-parent-&-back can also be implemented as an extension.
I'm thinking it'd make sense with both highlighting new comments, + a recent comments list.
(If relying only on [highlighting comments posted since the last page load], then sometimes one will miss a few recent comments — because usually one didn't read all comments shown on the page, but the next time the page gets reloaded, [previously shown but not-yet-read comments] will no longer be highlighted.)
This extension adds orange lines next to new comments since your last visit:
https://chrome.google.com/webstore/detail/hckr-news/mnlaodle...